Compaction by forestry equipment and effects on coniferous seedling growth on four soils in the Alberta foothills

Abstract

Soils developed on four parent materials (glaciolacustrine clay, clay loam till, coarse fluvial, and loamy eolian) in west-central Alberta were examined to determine residual effects of logging and use of site-preparation equipment upon soil bulk density. These studies were conducted on sites that were logged during the previous 24 years. Compaction was evident on all soils except those of the Summit association, which were dominantly Brunisolic Gray Luvisols developed on cobbly fluvial deposits of Tertiary age. Compaction was greatest on soils of the Marlboro association, which were dominantly Brunisolic Gray Luvisols developed on clay loam till. Soil bulk density values on the clear-cuts had recovered to those of the controls at comparable depth at ages ranging from 0 (Summit) to 17–21 years (Marlboro). Lodgepole pine and white spruce seedlings were grown on the four soils compacted in the laboratory to three bulk densities approximating the following field conditions: (1) those observed or expected immediately following logging and site preparation; (2) those observed 5–10 years after logging and site preparation; and (3) undisturbed control. In most cases, significant reduction in nine expressions of seedling growth (maximum root depth, maximum root depth in soil core, total weight, shoot weight, root weight, stem diameter, shoot height, seedling survival, and shoot weight: root weight ratio) was observed with increased bulk density.